Depending on where you are from, different countries have different terms for "storm drain".

Based on where you are from, different countries have different terms for "storm drain".
Accordingly to Wikipedia, a storm drain is actually a tunnel that carry runoffs (rain) from urban areas. For a layman, it helps to think along the line of sewage system that functions beneath our cities.
In america, this is actually often called "storm drain" or "storm sewer".
In the UK, this is actually best known "surface water drain" or "surface water sewer".
In Australia and New Zealand, it is typically referred to as "stormwater drain".
And there you have it, the next time you hear someone mentioning "storm drain", "storm sewer", "surface water drain","surface water sewer" and "stormwater drain", congratulations, you know they mean the exact same thing.
Functions of storm drain include draining excess water (rain or storm water) and ground water from pavement, streets and carparks into rivers and streams in order to avoid flooding.
Although storm drains perform a amazing job of draining excess water from the urban areas, the inlets are essentially openings where left uncovered could be a hazard to pedestrians. Left uncovered, rubbish will enter the storm drains and cause choking which might eventually lead to flooding.
To ensure storm drains serve their purposes while minimizing the risks posed to pedestrians and to prevent choking of the drains, drain covers (gratings) are widely-used to cover the inlets (openings) of driveway drain grates drains to achieve the two purposes.
Over at Jonite, we specialise in steel reinforced drain covers (gratings) that cover your storm drains while preserving the aesthetic areas of the architecture around the drain covers.